Method of consolidating an unconsolidated oil sand



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a-e States atent Qfifice latentecl June 18, 1968 1 2 3,388,743 tion of the gaseous oxidant also serves to disperse the METHOD OF CONSOLIDATING AN UNCONSOLIDATED OIL SAND Charles J. Engle, Bartlesville, Okla., and Melcon Santourian, Meshed, Iran, assignors to Phillips Ietroleum Company, a corporationof Delaware No Drawing. Filed Jan. 18, 1966, Ser. No. 521,416 v 9 Claims. (Cl. 166-11) ABSTRACT OF THE DISCLOSURE An unconsolidated sand is consolidated in an annulus adjacent a production well penetrating an oil stratum by depositing a slug of an autoignitable oil in said annulus, injecting a stream of oxidant gas (air) through an otfse-t well and through said stratum to said annulus at a rate sufi'icient to ignite oil therein, leave a coke residue in said annulus, and start an inverse burning combustion zone in said stratum.

This invention relates to a method or process for consolidating an unconsolidated oil sand around a well penetrating the sand.

When producing oil from an unconsolidated sand, production of sand in the production wells is a serious problem which .is recognized in the oil production art. The production of sand thru a production well is detrimental for a number of well-known reasons and is to be avoided whenever possible. Sand in the production stream is abrasive and injurious to equipment downhole as well as inthe recovery equipment required for separating the sand from the production stream.

This invention is concerned with a method for consolidating an unconsolidated sand around a production well so as to avoid sand production in the produced oil stream.

Accordingly, it is an object of the invention to provide a process for consolidating an unconsolidated oil sand around a production well penetrating the sand. Another object is to provide a simple procedure for consolidating an unconsolidated oil sand around a production well and elimination of sand production in the production stream. Other objects of the invention will become apparent to one skilled in the art upon consideration of the accompanying disclosure.

' A broad aspect of the invention comprises depositing an au-toignitable oil in a relatively narrow annulus of an unconsolidated sand around a well therein, injecting a stream of gaseous oxidant thru the annulus of deposited oil, and controlling the rate of oxidation of the oil so as to avoid burning out thereof and thereby consolidating the unconsolidated sand With partially oxidized oil as a binder. Oonventional'drying'oils, such as tung oil, linseed oil, soybean oil, tall oil, etc., function well in the process.

These oils, when partially oxidized, form a good binder for the sand grains. Their partial oxidation in the annulus of sand surrounding the well forms a relatively hard core which is highly permeable so that the hard annulus does not interfere with passage of fluids either from the surrounding sand into the well or from the well into the surrounding sand. Hence, the invention is applicable to either a production or an injection well.

The use of an oxidation catalyst such as lead or cobalt naphthenate, or any other suitable oxidation catalyst, in,

the injected oil inhances the process by reducing the time required for'the necessary partial oxidation of the oil.

While the oxidant gas may be injected immediately following the deposition of the autoignitable oil in the sand around the well, it is desirable to inject a relatively inert gas such as flue gas, CO or N to disperse the injected oil and render the oil-impregnated annulus permeable to the following oxidant flow. However, injecinjected oil and render the sand permeable.

The oxidation rate must be controlled so as to avoid ignition and burn-out of the injected oil. A thermocouple may be utilized downhole adjacent the sand and the rate of oxidant injection and/or the 0 concentration in the oxidant may be controlled to prevent excessive temperature rise which would indicate incipient combustion. When air is utilized as the oxidant, the flow rate of air should be maintained below about 15 standard cubic feet per hour per square foot of cross section of the impregnated sand face at the wallof the well. Flow rates in the range of about 3 to 15 standard cubic feet per square foot of cross section per hour are etfective in producing the desired oxidation of the oil. Another method of controlling the rate of oxidation so as to avoid burning comprises diluting air with a relatively inert, nondeleterious gas, such as flue gas, CO N etc., so that the oxygen concentration of the resulting mixture is in the range of about 5 to 18 volume percent.

After consolidating the sand around a well, the well may then be utilized as an injection well or as production well in any conventional fluid drive process. In the event the well adjacent the consolidated sand is to be produced as a production well in an inverse burning in situ combustion operation, air is injected thru one or more otfset wells while production is efiected thru the well containing the consolidated sand and, when the air reaches the innermost edge of the consolidated sand, ignition is efi'ected in the persence of reservoir oil so that the resulting combustion zone moves away' from the consolidated sand annulus toward the injection well(s). In order to aid in the ignition phase of the process after the consolidated annulus is formed, additional autoignitable oil may be injected thru the permeable consolidated annulus followed by driving the oil thru the annulus with either an inert gas or a petroleum oil or fuel miscible with the autoignitable oil and ranging from gasoline to light gas oil, or even crude oils, having relatively low ignition points. Bellridge crude is such an oil. The autoignitable oil injected after the consolidation process must be driven thru the consolidated annulus so as to preserve the binder during the followingignition and production steps. 1

i The following specific examples are presented to illustrate the invention and are not to be construed as unnecessarily limiting the same.

In one test, 49 g. of flint shot Ottawa sand were mixed with 4 g. of tung oil and packed in a Gooch crucible. Using a Vacuum flask, air was pulled thru the oil-impregnated sand and after about 24 hours the sand was set and firmly bound into a solid mass by the partially oxidized oil.

In another test, a similar sample of oil-impregnated sand was prepared with 0.1 cc. of cobalt naphthenate mixed with the tung oil as a catalyst. Using the same air flow procedure, this sample hardened in about 4 hours to form a firmly bound mass of sand.

The sand plugs produced by the foregoing tests were removed from the crucible and subjected to high-temperature gas flow ranging up to 600 F. and held at this maximum temperature for 2 hours. The consolidated sand plugs withstood this maximum temperature; however, oxidation at higher temperatures caused the partially oxidized binder to burn out, leaving a relatively loose sand.

In consolidating a sand around the well, the porosity of the sand, sand thickness, and desired size (volume) of the annulus to be consolidated determine the amount of oil to be injected. The available sand porosity, in particular, is a factor in determining the amount of oil to be injected.

Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention- We claim:

1. A process for consolidating an unconsolidated sand around a production well penetrating said sand which comprises the steps of:

(1) depositing a slug of an antoignitable oil in a relatively narrow annulus of said sand surrounding said production well;

(2) injecting a stream of oxidant gas thru an offset injection Well into and thru said annulus in contact with the deposited oil;

(3) controlling the rate of oxidation of said oil so as to avoid burning out of the oil and to consolidate said sand with the partially oxidized oil as a binder; and

(4) continuing step (2) so as to initiate combustion of in-place oil and cause a resulting combustion zone to move toward said offset well.

2. The process of claim 1 wherein said oil is a member of the group tung oil, linseed oil, soybean oil, and tall oil.

3. The process of claim 1 wherein said gas is air.

4. The process of claim 1 wherein said gas is a mixture of air with a non-oxidizing, relatively inert gas and the mixture has an concentration in the range of about 5 to 18 percent by volume.

5. The process of claim 1 wherein said gas is air and the fiow rate is maintained below about 15 standard cubic feet per hour per square foot of cross section of annulus.

6. The process of claim 1 wherein an inert gas is injected thru said annulus intermediate steps (1) and 2) to disperse said oil and to render said annulus permeable.

7. The process of claim 1 wherein an oxidation catalyst in a minor but effective concentration is incorporated in the annulus in admixture with the deposited oil.

8. The process of claim 7 wherein said catalyst is cobalt naphthenate.

9. The process of claim 1 including the steps of:

(5) injecting a second slug of autoignitable oil, thru said production well into the consolidated annulus subsequent to step (3) and prior to step (4); and

(6) driving said second slug thru said annulus by fluid drive using a fluid driving lmedium other than an autoignitable oil so as to substantially free said annulus of said second slug of oil.

References Cited UNITED STATES PATENTS 3,003,555 10/1951 Freeman et al 166-11 X 3,044,546 7/1962 Dixon 166-25 X 3,134,435 5/1964 Wyllie 166-25 3,147,805 9/1964 Goodwin et al. 166-25 3,180,412 4/1965 Bedmarski et a1. 16638 X 3,205,944 9/1965 Walton 1661l 3,217,800 11/1965 Smith 166-25 3,254,716 6/1966 Fitzgerald et al. l6625 3,292,701 12/1966 Goodwin et al. 166-25 STEPHEN I. NOVOSAD, Primary Examiner. 

